Does it really work? Doesn the heated water just flow upwards in the hose for the sink?
Yes – the heated water does rise to water-line level in the hose where it comes to a stand-still before rocking up-and-down. This, however, has no influence on the cooling effect as an equal volume of water as that rocking up-and-down flows in-and-out through the heat exchanger situated in the skin fitting. Here, every single movement – large or small – of the boat’s hull in the water pumps in the same volume of cold water into the heat exchanger as the volume of heated water that has just been sucked out. It is precisely at the orifice of the skin fitting where the heat exchange action occurs – not in the water standing higher up in the hose to the sink. It is for this reason that the inside diameter of the hose at water-line level must be a minimum of 1.5″ while that of the orifice in the skin fitting is only 1″ diameter. The resultant 2:1 area differential is very important as it creates an appreciable amount of additional turbulence in the orifice.
